The results were so surprising that study co-author Juan Sanchez-Ramos didn't believe them at first.

"It's such a dramatic and counterintuitive effect," said Sanchez-Ramos, a University of South Florida neuroscientist.

"I joked that the animals must have been mislabeled or that the power wasn't switched on."

Cell Phones Provide Protective Radiation?

The primary culprits in Alzheimer's disease—which is marked by dementia and cognitive decline—appear to be sticky brain deposits known as beta amyloid plaques, which can build up between nerve cells.

In the experiment, scientists examined the effects of cell phone radiation on 96 mice that were genetically engineered to develop beta amyloid plaques and thus Alzheimer's-like symptoms. The mice normally developed the first signs of the disease around 6 months. By 8 months they were already experiencing cognitive declines.

Both the Alzheimer's-prone mice and normal mice were then exposed to cell phone-level microwave radiation for two one-hour periods daily for seven to nine months.

The study found that if cell phone exposure began before the genetically engineered mice started showing signs of Alzheimer's, they were less likely to develop symptoms later on in life.

These mice performed as well on memory and thinking-skills tests as normal mice without Alzheimer's. For instance, the mice were given a cognitive interference task that tested their ability to remember something after an interruption. The team also put the mice through a three-armed Y maze, which measures basic memory function.

Furthermore, the genetically engineered mice that were were exposed to the cell phone radiation after they had already begun to show cognitive deficits generally saw their memory impairment disappear after several months of the radiation exposure.

Of Mice and Men and Alzheimer's

No one knows how the radiation protects against Alzheimer's, but the team has some ideas.

One is that the microwaves create cellular stress in the brain, and that the stress jump-starts DNA repair mechanisms in the brain.

For instance, scientists already know that "minor insults" such as toxic substances or low oxygen will improve the brain's ability to repair damage to proteins and DNA, Sanchez-Ramos said.

However he cautioned that the experiment was not "a perfect replication of cell phone use in humans."

For instance, the lab mice were exposed to cell phone radiation over their entire bodies—not just to their heads.

"It's an interesting finding and perhaps it could be translated somehow to a human test," said David Knopman, an Alzheimer's expert at the Mayo Clinic in Rochester, Minnesota.

But he also urged caution against assuming the findings would apply to humans.

"What goes on in mice may not have anything to do with people," said Knopman, who did not participate in the study.

"This animal model of Alzheimer's is useful, but there's still many questions about whether it's ultimately valid [to humans] or not."

That's because Alzheimer's disease does not manifest itself in the same way in humans, said George Perry, an Alzheimer's expert at the University of Texas, San Antonio, who was not involved directly with the research.

"In most people, the development of amyloid plaques is related to the aging process—not because they're genetically modified," Perry said.

Not All Bad?

Nevertheless, the "pretty dramatic" research raises the possibility that health effects of cell phone radiation are not all harmful, added Perry, who is also editor in chief of the Journal of Alzheimer's Disease, in which the January 6 study was published.

Some scientists, for instance, claim that cell phones can lead to increased risks of brain cancer. Such concerns have led the U.S. state of Maine to consider requiring that cell phones carry warning labels.

The new study, though, "puts the debate in a perspective where we need to consider a broad range of effects of cell phone radiation," Perry said.